1. Field of the Invention
The present invention relates to submersibles used for exploration of the sea or other purposes.
2. Description of the Prior Art
In the submersibles used for oceanographic investigation or other purposes, a fluid such as sea water is fed and discharged into and from buoyancy tanks provided in the hull to increase and decrease the weight of the hull when the submersible cruises underwater or surfaces, thereby increasing and decreasing the specific gravity of the hull. In the case of attitude control of the hull while the submersible is under water, a quantity of mercury contained in trimming tanks provided at the front and rear portions of the hull is increased and decreased so that the center of gravity of the hull is transferred beneath the center of buoyancy. When the submersible cruises underwater, a screw propeller is driven through a storage battery to obtain propulsive force.
It has recently been desired to commercially produce submersibles suitable for the maintenance of submarine oil fields, oceanographic investigations in relatively shallow sea areas, fishing ground search, the works at so-called sea stock farms, submarine transportation, and other purposes. However, the conventional submersibles have the following disadvantages which make it difficult to meet the above-mentioned needs. Firstly, the submersible largely depends upon the buoyancy tanks in the movement thereof under water. The buoyancy &tanks are required to be rendered larged-sized so that the submersible is designed to be large-scaled, to be capable of being loaded with various equipments, or to transport a large amount of cargo. Accordingly, the submersible hull is caused to be more and more large-scaled. As the hull is large-scaled, the propeller is also rendered large-scaled, resulting in increasing of the weight of the storage battery. Additionally, the submersible necessitates another buoyancy tank in order that the heavy equipments or collections may be transported from one place to another under water. As a result, the hull of the submersible is required to be rendered large scaled. Furthermore, a large quantity of mercury for the adjustment of the center of gravity of the hull needs to be contained in the front and rear trimming tanks so that the submersible can be loaded with articles or goods under water. In the case of the attitude control by means of mercury containing trimming tanks, the front and rear trimming tanks are communicated to each other by a pipe, and the mercury is transferred between the front and rear tanks through the pipe. As a result, rotation moment is induced to the hull. When the hull is controlled to be maintained at the horizontal position, the transportation of mercury is caused to stop, whereby the hull is maintained at the horizontal position, and consequently, the center of gravity of the hull is positioned beneath the center of buoyancy. The quantity of mercury is increased where the cargo loaded is located, for example, on an edge portion of the hull for the sake of convenience in loading and unloading the cargo. Accordingly. the weight of the hull is necessarily increased, resulting in increase of the frictional resistance of the hull and therefore, reduction of the underwater cruising capacity.
Secondary, the conventional submersible employs the construction that the screw propeller for the underwater cruise is driven through a storage battery. The storage battery usually has a large weight, and a large-sized storage battery causes the buoyancy of the hull to be large. Consequently, the hull is further rendered large-scaled.